Wrangel Island - Geology

Geology

Wrangel Island consists of folded, faulted, and metamorphosed volcanic, intrusive, and sedimentary rocks ranging in age from Upper Precambrian to Lower Mesozoic. The Precambrian rocks, which are about 2 km (1.2 mi) thick, consist of Upper Proterozoic sericite and chlorite slate and schist that contain minor amounts of metavolcanic rocks, metaconglomerates, and quartzite. These rocks are intruded by metamorphosed gabbro, diabase, and felsic dikes and sills and granite intrusions. Overlying the Precambrian strata are up to 2.25 km (1.4 mi) of Upper Silurian to Lower Carboniferous consisting of interbedded sandstone, siltstone, slate, argillite, some conglomerate and rare limestone and dolomite. These strata are overlain by up to 2.15 km (1.34 mi) of Carboniferous to Permian limestone, often composed largely of crinoid plates, that is interbedded with slate, argillite and locally minor amounts of thick breccia, sandstone, and chert. The uppermost stratum consists of 0.7 to 1.5 km (0.43 to 0.93 mi) of Triassic clayey quartzose turbidites interbedded with black slate and siltstone.

A thin veneer of Cenozoic gravel, sand, clay and mud underlie the coastal plains of Wrangel Island. Late Neogene clay and gravel, which are only a few tens of meters thick, rest upon the eroded surface of the folded and faulted strata that comprise Wrangel Island. Indurated Pliocene mud and gravel, which are only a few meters thick, overlie the Late Neogene sediments. Sandy Pleistocene sediments occur as fluvial sediments along rivers and streams and as a very thin and patchy surficial layer of either colluvium or eluvium.